Ozone bond angle

Once you have completed this first calculation, devise and run calculations which will determine the lowest energy electronic state for ozone. Use the experimental geometry 0-0 bond lengths=1.272 A, 0-0-0 bond angle=116.8 . 

Predict the bond angles at the central atom of the following molecules and ions (a) ozone, 03 (b) azide ion, N3 ... 

We begin our exploration of delocalized bonds with ozone, O3. As described in Chapter 7, ozone in the upper stratosphere protects plants and animals from hazardous ultraviolet radiation. Ozone has 18 valence electrons and a Lewis stmcture that appears in Figure 10-36a. Experimental measurements show that ozone is a bent molecule with a bond angle of 118°. 

For dissociation at 226 and 230 nm, the determined j3 values for the fast and slow oxygen atoms are 1.3/1.5 and 0.7/0.8, respectively. The former value corresponds to a bond angle of 120°, close to the ozone ground state equilibrium bond angle of 117°. The reduced anisotropy parameter of 0.8 implies a more strongly bent geometry with a bond angle of 100°. 

The structure of ozone 21, after a long period of uncertainty, is now probably as indicated, with a bond angle of 126° and a bond length 1.26 A ozone has a dipole moment of 0.49 D. The following four configurations contribute so that the O—O distance lies between those of a single and of a double bond (1.46 A and 1.10 A). 

Such a five-membered cyclic transition state has been proposed for the triiodide cleavage of carbon-mercury bonds (2). While such a structure is unlikely for the linear I3 ion, it should easily accommodate the ozone molecule whose bonding angle is 116° (12). Of course the geometrical plausibility of Structure 27 depends on the degree of carbon-mercury... 

O3 Ozone 127.8 Bond angle 116.8° strong oxidizing agent absorbs in UV (below 320 nm)... 

Figure 3 Two-dimensional representations of the ground-state PES of ozone. Ri and R2 are the bond distances between the central atom and the two end atoms and a is the 000 bond angle. The inset shows the potential along the minimum energy path. Reproduced, with permission of The Owner Societies, from Ref. 42.

Since the standard free energy of formation of ozone is a large positive quantity (AG = (326.8/2) kJ/mol or 163.4 kJ/mol), ozone is less stable than molecular oxygen. The ozone molecule has a bent structure in which the bond angle is 116.5° ... 

Ozone is a triangular molecule with a bond distance of 1.27 A, and a bond angle of 117°. This could be compared with the bond distance in the double bonded O2 molecule, 1.21 A, or to the single bond in HOOH, 1.46 A. We conclude that partial double bonds are formed between the end and central oxygen atoms. How can we explain this One would expect the ozone molecule to be a bi-radical because the end atoms can only use one of their free valencies to form a bond with the central atom. But ozone is not a biradical, even if it is quite reactive. The radical structure is quite high in energy and there are ionic structures that may compete. We show the three most important valence structures in Fig. 25.6. 

The ozone molecule is known to have a bond angle close to 120°. Recall that 120° angles represent the minimum repulsion for three pairs of electrons. 

What are the Lewis structures for the two allotropic forms of oxygen How can the paramagnetism of O2 be explained using the molecular orbital model What are the molecular structure and the bond angles in ozone ... 

For example, rotation of the ozone molecule by 180 around an imaginary axis that bisects the 0-0-0 bond angle leads to an equivalent configuration for the molecule. In each case, there is one 0-0 single bond and one 0=0 double bond in the contributing canonical structures the only difference between them is the placement of the single and double bonds. Likewise, in the carbonate ion, rotation of each subsequent canonical structure by 120° or 240° leads to a structure that is identical to the original. As we see in a later chapter, symmetry plays an important role in the structure and physical properties of molecules. 

Because we start with three atomic orbitals, we can construct three molecular orbitals. The general procedure for determining the values of the coefficients Ca, Cb, and Cq for these three molecular orbitals is mathematically involved in the present case, however, we can use what we know about the symmetry of the problem and the general behavior of electron wavefunctions to obtain a very good qualitative picture of the molecular orbitals. First, the ozone molecule is symmetric, with a mirror plane bisecting the O—O—0 bond angle. Reflection of the molecular orbital through this... 

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